// Copyright (c) 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "cc/output/context_cache_controller.h"

#include "base/bind.h"
#include "base/logging.h"
#include "base/memory/ptr_util.h"
#include "base/synchronization/lock.h"
#include "gpu/command_buffer/client/context_support.h"
#include "third_party/skia/include/gpu/GrContext.h"

namespace cc {
namespace {
    static const int kIdleCleanupDelaySeconds = 1;
} // namespace

ContextCacheController::ScopedToken::ScopedToken() = default;

ContextCacheController::ScopedToken::~ScopedToken()
{
    DCHECK(released_);
}

void ContextCacheController::ScopedToken::Release()
{
    DCHECK(!released_);
    released_ = true;
}

ContextCacheController::ContextCacheController(
    gpu::ContextSupport* context_support,
    scoped_refptr<base::SingleThreadTaskRunner> task_runner)
    : context_support_(context_support)
    , task_runner_(std::move(task_runner))
    , weak_factory_(this)
{
    // The |weak_factory_| can only be used from a single thread. We
    // create/destroy this class and run callbacks on a single thread, but we
    // want to be able to post callbacks from multiple threads. We need a weak
    // ptr to post callbacks, so acquire one here, while we're on the right
    // thread.
    weak_ptr_ = weak_factory_.GetWeakPtr();
}

ContextCacheController::~ContextCacheController() = default;

void ContextCacheController::SetGrContext(GrContext* gr_context)
{
    gr_context_ = gr_context;
}

void ContextCacheController::SetLock(base::Lock* lock)
{
    context_lock_ = lock;
}

std::unique_ptr<ContextCacheController::ScopedVisibility>
ContextCacheController::ClientBecameVisible()
{
    if (context_lock_)
        context_lock_->AssertAcquired();

    bool became_visible = num_clients_visible_ == 0;
    ++num_clients_visible_;

    if (became_visible)
        context_support_->SetAggressivelyFreeResources(false);

    return base::WrapUnique(new ScopedVisibility());
}

void ContextCacheController::ClientBecameNotVisible(
    std::unique_ptr<ScopedVisibility> scoped_visibility)
{
    DCHECK(scoped_visibility);
    scoped_visibility->Release();

    if (context_lock_)
        context_lock_->AssertAcquired();

    DCHECK_GT(num_clients_visible_, 0u);
    --num_clients_visible_;

    if (num_clients_visible_ == 0) {
        // We are freeing resources now - cancel any pending idle callbacks.
        InvalidatePendingIdleCallbacks();

        //     if (gr_context_)
        //       gr_context_->freeGpuResources();
        DebugBreak();
        context_support_->SetAggressivelyFreeResources(true);
    }
}

std::unique_ptr<ContextCacheController::ScopedBusy>
ContextCacheController::ClientBecameBusy()
{
    if (context_lock_)
        context_lock_->AssertAcquired();

    ++num_clients_busy_;
    // We are busy, cancel any pending idle callbacks.
    InvalidatePendingIdleCallbacks();

    return base::WrapUnique(new ScopedBusy());
}

void ContextCacheController::ClientBecameNotBusy(
    std::unique_ptr<ScopedBusy> scoped_busy)
{
    DCHECK(scoped_busy);
    scoped_busy->Release();

    if (context_lock_)
        context_lock_->AssertAcquired();

    DCHECK_GT(num_clients_busy_, 0u);
    --num_clients_busy_;

    // If we have become idle and we are visible, queue a task to drop resources
    // after a delay. If are not visible, we have already dropped resources.
    if (num_clients_busy_ == 0 && num_clients_visible_ > 0 && task_runner_) {
        // If we already have a callback pending, don't post a new one. The pending
        // callback will handle posting a new callback itself. This prevents us from
        // flooding the system with tasks.
        if (!callback_pending_) {
            {
                base::AutoLock hold(current_idle_generation_lock_);
                PostIdleCallback(current_idle_generation_);
            }
            callback_pending_ = true;
        }
    }
}

void ContextCacheController::PostIdleCallback(
    uint32_t current_idle_generation) const
{
    task_runner_->PostDelayedTask(
        FROM_HERE, base::Bind(&ContextCacheController::OnIdle, weak_ptr_, current_idle_generation),
        base::TimeDelta::FromSeconds(kIdleCleanupDelaySeconds));
}

void ContextCacheController::InvalidatePendingIdleCallbacks()
{
    base::AutoLock hold(current_idle_generation_lock_);
    ++current_idle_generation_;
}

void ContextCacheController::OnIdle(uint32_t idle_generation)
{
    // First check if we should run our idle callback at all. If we have become
    // busy since scheduling, just schedule another idle callback and return.
    {
        base::AutoLock hold(current_idle_generation_lock_);
        if (current_idle_generation_ != idle_generation) {
            PostIdleCallback(current_idle_generation_);
            return;
        }
    }

    // Try to acquire the context lock - if we can't acquire it then we've become
    // busy since checking |current_idle_generation_| above. In this case, just
    // re-post our idle callback and return.
    if (context_lock_ && !context_lock_->Try()) {
        base::AutoLock hold(current_idle_generation_lock_);
        PostIdleCallback(current_idle_generation_);
        return;
    }

    //   if (gr_context_)
    //     gr_context_->freeGpuResources();
    DebugBreak();

    // Toggle SetAggressivelyFreeResources to drop command buffer data.
    context_support_->SetAggressivelyFreeResources(true);
    context_support_->SetAggressivelyFreeResources(false);

    callback_pending_ = false;

    if (context_lock_)
        context_lock_->Release();
}

} // namespace cc
